This is from an email exchange. I was supposed to meet with someone and asked the person how long our (future) meeting would last. The response was "I was thinking we talked for 30 min".
It occurred to me that while I knew the meaning of it, it had been a while since I learned the relevant grammar rule, so I couldn't "justify" the usage of past simple in this sentence. I tried googling, but haven't found anything relevant yet.
My confusion is about using past tense to describe a future event. It sounds like an effort to make it sound more tentative and more polite, perhaps. Something in the spirit of "I'd prefer (it) if you didn't mention this to anyone." but I can't quite pinpoint the relevant grammar here. Or was it just a mistake?